1. Field of the Invention
The present invention relates to an image fixing apparatus for fixing a toner image onto a recording medium by heating the recording medium and the toner thereon.
2. Description of the Related Art
In an image fixing apparatus mounted in a copy machine or a printer using an electrophotographic recording technique, a fixing rotation member for forming a fixing nip portion of the image fixing apparatus gets dirty due to a toner component which is not fixed onto a recording medium. Therefore, a device for cleaning the fixing rotation member by bringing a web in contact with a peripheral surface of the fixing rotation member to wipe off the toner component adhered to the peripheral surface of the fixing rotation member with the web has been utilized.
In Japanese Patent Application Laid-Open No. H08-220921, an image fixing apparatus which stretches a web (cleaning web 16) wound around a supplying roller (feeding roller 25) over a winding roller (press rolling roller 26) is described. In this technique, since the winding roller itself also serves as a contact roller and presses a fixing rotation member (heating roller 12) with the web to form a cleaning nip portion, cleaning of the fixing rotation member can be performed only by the winding roller and the supplying roller. During the cleaning, the winding roller is rotated to draw an unused portion for cleaning of the web into the cleaning nip portion and roll up a used portion for cleaning around a peripheral surface of the winding roller.
Although heating of the fixing rotation member performed by a heating member (heater 11) is stopped, the fixing rotation member does not immediately cool. Therefore, as long as the winding roller is pressed by the fixing rotation member with the web, the web near the cleaning nip portion is in the state of being heated by the fixing rotation member for a while even after the heating is stopped. Since the used portion for cleaning of the web is rolled up around the winding roller, the used portion for cleaning of the web is layered in the vicinity of the cleaning nip portion and nipped between the fixing rotation member and the winding roller. Accordingly, in the vicinity of the cleaning nip portion after the heating is stopped, a toner component inside the web of a layer (surface layer) which comes in contact with the fixing rotation member is in a high-fluidity state. Moreover, even a toner component that hardens inside the web of a layer (lower layer) which is closer to a peripheral surface of the winding roller than the surface layer becomes softened. This is because a time for heat remaining in the fixing rotation member to transfer to the web of the lower layer is shorter than a time for the fixing rotation member to cool to a temperature at which fluidity of the toner component is sufficiently decreased. As a result, in the vicinity of the cleaning nip portion which is pressed, the toner component held between the web of the surface layer and the web of the lower layer is exuded, thereby degrading a cleaning ability of the web.
Furthermore, in a case where the apparatus is configured so that the supplying roller whose peripheral surface is rolled with the unused portion for cleaning of the web also serves as the contact roller, only the web of the surface layer holds the toner component therein in the vicinity of the cleaning nip portion, and the unused portion for cleaning of the web of the lower layers other than the surface layer are overlapped. Therefore, in the vicinity of the cleaning nip portion after the heating is stopped, the toner component inside the web of the surface layer that comes in contact with the fixing rotation member is in the high-fluidity state, so that the toner component permeates and flows into the unused cleaning web of the lower layers, thereby degrading the cleaning ability of the web.